Altman, one of the most influential and idiosyncratic of American filmmakers, died Monday of complications due to cancer at Cedars-Sinai Medical Center in Los Angeles. He was 81.

He owed his longevity and the distinctiveness of his style to his refusal to work for the major studios. He secured independent financing for his films and sought a distributor only after the movie was finished.

Few of his films were hits, but — and this is something few major filmmakers can say — they were all his.

"All my films, as I look back, I see they're just chapters of the same book," he said in an interview with the Chronicle in 2000. "The first five, 10, 15 films I made, I thought, 'Man, nobody will ever know that this film came from me. They're all so different.' ... But I look now and I see my fingerprints are all over them. I think you can't help that."

He made more than 30 movies. More than a handful, including The Player and Short Cuts, are considered classics. But even his lesser-known body of work includes sublime treasures.

Born in Kansas City, Mo., in 1925, Altman first made a name for himself in television, directing for such shows as Bonanza and Combat! He made two movies in the late 1960s, as his television career wound down. Then, in 1970, came M*A*S*H, his first hit and still his most financially successful film.

Here, for the first time, were the hallmarks of a style that later would be known as Altmanesque — overlapping dialogue, a large cast, sardonic humor, compassion for the underdog and an episodic structure with only the barest hint of a story.

He followed it with Brewster McCloud, a quirky comedy about a boy who secretly lived in the bowels of the Astrodome and yearned to fly.

"He had the world spread out before him," said Jeff Millar, a former Chronicle movie critic who came to know Altman during the period, "but he decided to make this little uncommercial film. He continued to make uncommercial films for the rest of his life."

At a party here, Altman met Shelley Duvall, who sold cosmetics at Foley's. He cast her in the movie. She went on to star in six more films for Altman. Also getting his start with McCloud was Gary Chason, a Houston theatrical director whom Millar introduced to the director. McCloud was the start of Chason's career as a casting director for such movies as Paper Moon, Pretty Baby and Paris, Texas.

Altman adored the South for its distinctiveness. He made four movies in Texas and also filmed in Mississippi, Georgia and Florida. Many of his films set in other locations had Southern characters. In Prêt-à-Porter, set in France, Julia Roberts played a fashion editor for the Chronicle.

Millar recalled taking the director to a meal at Phil's Diner in Montrose. "It was a tiny hole in the wall with a plate lunch for something like $1.39."

"He was just a charming, jovial person who was extremely personable and had no affectations from Hollywood that you could ever probably imagine."

Altman encouraged actors to improvise and, more than most directors, allowed his movies to develop organically.

"There were hard truths in his films, and life was allowed to retain its cruelty and its candor," said musician Tom Waits, who appeared in Altman's Short Cuts.

Sometimes the results of this creative chaos were awful. Witness Dr. T and the Women, the last movie he shot in Texas. The riskiness of his approach meant that even his better movies weren't sure things.

"I almost worked with him," Bob Newhart told the Chronicle. "I was doing Catch 22 and was offered a part in M*A*S*H. I read the script, and to me it was episodic and just didn't work. ... As I understand it, when they got through and started putting the movie together, it didn't work. They said, 'Hey, this doesn't make sense.' Then they put in the guy making the announcements (in the background), and it was in that dispassionate voice over the loudspeaker, and that apparently pulled it together. It made it funny."

Altman's last movie, released earlier this year, was A Prairie Home Companion. A fictionalized tale about the last days of the famous radio program, it is a death-haunted work that features the Angel of Death and the demise of more than one character. Altman learned he had cancer 18 months ago, meaning he started making the film while ill.

Because of Altman's age and health, Paul Thomas Anderson, a filmmaker greatly influenced by Altman, worked as "back-up" director on the movie. Yet, in March, when Altman accepted a Lifetime Achievement Award from the Academy of Motion Picture Arts and Sciences, he quipped, "I've always thought this type of award meant it was over. I think I've got 40 years left on it."

Meryl Streep, who starred in Prairie Home Companion, said she recently talked with Altman about making another movie together.

"I have to say, when I spoke with him last week, he seemed impatient for the future," she said in a statement. "He still had the generous, optimistic appetite for the next thing, and we planned the next film laughing in anticipation of the laughs we'd have. What a gent, what a guy, what a great heart. There's no one like him, and we'll miss him so."

"I'm sorry that our movie turned out to be his last," said Garrison Keillor, the creator of the Prairie Home Companion radio program, "but I do know that he loved making it.

"Mr. Altman loved making movies," Keillor said. "He loved the chaos of shooting and the sociability of the crew and actors — he adored actors — and he loved the editing room, and he especially loved sitting in a screening room and watching the thing over and over with other people. He didn't care for the money end of things, but when he was working, he was in heaven."

Altman is survived by his wife, Kathryn Reed Altman, and six children, 12 grandchildren and five great-grandchildren.